ycgoat

I have the body off and down to just the original rolling chassis and was going to mach up the engine and transmission, I have the original 455 and an LQ4, so I was going to connect a 4l80 to the 455 to locate the transmission cross member then connect the 4l80 to the Lq4 and mount it. My concern is the pinion angle. Since I will be replacing the suspension and lowering the car, do I need to replace the suspension and set it up with the body on to set the ride height before I can locate the drive train and pinion angle?

1981TA

iTrader: (7)

I did roughly the same thing and simply had to make sure the Trans to driveshaft angle was equal and opposite the axle to driveshaft angle. Most of the decent custom driveshaft makers have basic instructions for this online. You will also find sage advice in the transmission and drive train forums here.

Project GatTagO

iTrader: (7)

Unfortunately A-bodies have notoriously small transmission and driveshaft tunnels. When you swap in a LS engine and also lower the car, the driveline issue really becomes a problem even when using adjustable rear upper control arms.

With the adjustable control arms, you will be able to make the front and rear u-joint operating angles equal and opposite, but the resulting angle will be too large for high speed operation. The operating angles should be kept as small as possible (definitely under 3 degrees), but not zero.

My recommendation is to get the engine down at the motor mounts as low as possible and raise the back of the transmission as high as the body will allow it. Even then the front operating angle may be over 3 degrees with a lowered car. Currently my front operating angle is about 6 degrees. I solve this by using a driveshaft with a CV joint (Rzeppa style CV) at the transmission.

This is one of those dirty little secrets of doing a LS swap on an a-body.

Andrew

ycgoat

Thanks, that lead me to the Drive Shaft Shop. So can I set the LS on the old rolling chassis make the trans and diff parallel and fine tune the angle during final assembly after new suspension?

Project GatTagO

iTrader: (7)

Probably. Just get the engine as low as you can at the front crossmember. Use the new Holley pan for extra tie rod clearance and mounts that place the engine as low as possible (not sure which ones do that). Put the trans on the stock trans crossmember, knowing that you might need to adjust the height once the body is back on.

If you can figure out the position of the rear axle at ride height, and use tubes in place of springs and shocks, that should give you a good idea of what you're working with. Hope that makes sense.

Andrew

ycgoat

yes it does thanks.

kwhizz

What he said!!!!!

thunderstruck507

iTrader: (18)

Agree...I had mine resting on the crossmember and the result was a severe downward angle on the transmission. I used longer bolt and put a 1" thick spacer between the transmission mount pad on the crossmember and the mount itself. (by spacer I mean a pair of big *** nuts).

This does make it a requirement to massage the tunnel...BFH or cut a relief and weld in metal to open it up more like t56 swap cars do.

ycgoat

Thanks, I have plenty of sheet metal work to do in that area.

Project GatTagO

iTrader: (7)

Just be prepared for the fact that even with making a new transmission tunnel, you may not be able to get the back of the transmission up high enough to have an acceptable front u-joint operating angle. This is because the slip yoke will be in the way of the driveshaft tunnel.

Please post back and let us know how this goes.

Andrew